Trace material analysis has many applications in biochemistry, medicine, homeland security, environmental science and other related fields. Accordingly, there is great interest in finding ways to rapidly characterize trace materials and to assess their molecular dynamics. Trace materials containing fluorescent and/or phosphorescent molecules may be identified uniquely or within a class by measuring their steady-state emission spectra.
Fluorescence flux at a specific emission wavelength may be measured by using an intensity-modulated laser light source in combination with a time-resolved single-detector system and a monochromator. The monochromator-based single-detector system, however, does not provide high optical throughput. Low throughput results in lowered signal-to-noise ratio and increased data acquisition times. Long acquisition times are undesirable, particularly where unstable or fragile molecular systems are concerned.
Fluorescence may also be measured using a dispersive instrument incorporating a detector array. Multiple emission wavelengths may be acquired in parallel, with temporal resolution possible in each spectral bin given adequate detector-array response time. The dispersive/detector-array system may allow for more rapid data acquisition than the monochromator-based system, but can suffer from inadequate detector array response time. Thus it can be difficult to characterize the temporal response of each spectral bin to assess the molecular dynamics of some fluorescent systems. The dispersive/detector-array system also can suffer from poor optical throughput, thus further limiting its efficacy relative to weakly emitting trace materials. Calibrating the dispersive detector-array system typically is complex. Each detector element is a distinct sensor which must be calibrated to minimize critical detector-to-detector response error.